Process for preparing propellant powder



dough.

die. presses, rolls, and other explosive treating equipment lant and facilitates the extrusion of the mixture.

PROCESS FOR PREPARING PROPELLANT I POWDER Chemical Corporation, a corporation of Virginia No Drawing. Application April 11,1951 Serial No. 220,530

7 Claims; (cr sz-zo This invention relates to the manufacture of propellent explosive and more particularly to the production of extruded powder grains.

Conventional methods of producing extruded powder grains for use in ammunition in small arms and cannons has ordinarily involved colloiding the nitrocellulose base with a volatile solvent mixture to form an extrudable Such methods involved elaborate and costly technique for removing the volatile solvent from the extruded powder grains. In the manufacture of giant grains, for instance several inches in diameter and over nited 6 patmto a foot long such as are used for rocket powder, gelatinization of the nitrocellulose was effected by coiloiding on heated rolls with frequent intermediate kneading operations. The resulting sheet or carpet of explosive was then rolled into a bundle and inserted in the. extruding Such a process has the disadvantage that huge capable of producing extremely high pressures are re quired, and the operation is, at best, very slow and hazardous, requiring many precautions to avoid explosion during the colloiding process. Furthermore, when the composition contains nitroglycerine, considerable nitrosive rolling and kneadingresulting in variations in com position of the ultimate grains. Further disadvantages are that the process is batch-wise resulting in considerable down time .for the equipment, and a large quantity of scrap is produced, since the last material from each individual carpet roll that is extruded and the first of the next roll are not usable.

The present invention has as an object the provision of a simplified and improved process for manufacturing extruded powder grains whereby the aforementioned and other disadvantages of prior extruding processes are overcome. Another object of this invention is to provide a process for'producing extruded powder grains of either single or double base composition in which volatile solvents and the use of rolling, kneading, and other high pressure mixing methods and devices are eliminated. A further object is to provide an improved process for extruding powder grains of any desired size, and particularly suited for the production of grains of rocket powder size.

The foregoing objects and advantages as well as others which will become apparent from the following detai ed description, are accomplished in accordance with this invention, generally stated, by providing particles or pellets of a propellant, uniformly mixing therewith a plastisol solvent in a sufficient amount to provide a pourable and fiowable paste, heating the paste to an elevated temperature to cause the plastisol solvent to dissolve the propellant, extruding the heated mass through a die in a continuous piece and subdividing the extruded piece or rod into the desired lengths for powder grains. The

elevated temperature hastens the solution of the propelplastisol solvent as used herein is meant a relatively glycerine may be lost by volatilization during the exten- 2,917,319 Patented Dec." 15, v195 9 non-volatile liquid which is a slow acting solvent or one having only little ,or no solvent powder for the particles of propellant at low or ordinary room temperatures, but

. being rapidly acting and having a relatively great solvent spherical pellets of highdensity in US. Patent 2,160,626. 7 Such, spheres are particularly advantageous in the present invention because of their inherent characteristic of being relatively free-flowing. even in the dry state, and because of their case-hardened surface characteristics which tends to 1 resist initial attack by the solvent. This surface characteristic is undoubtedly the result of a skin effect occasioned by surface tension and removal of the solvent in the formation of the spheres. Other ingredients, such as dioctyl phthalate, lead stearate, red lead, centralite, carbon black, dinitrotoluene, and the like, may be incorporated with the nitrocellulose in the formation of the spherical pellets to obtain particular ballistic properties as desired. Using such spherical particles, at relatively free-flowing paste is obtained in accordance with this invention when the spheres are 'mixed with the proper proportion of the pfastisol solvent, whereas if irregular shaped particles, such as may be obtained by merely grinding cannon powder or the like, are utilized, the desirable free-flowing characteristics of the paste are not obtained. Although the spheres of propellant may be of any desired size, large diameter spheres require. relatively longer periods of time in order to effect their solution and resultant solidification of the grain, whereas with smaller spheres, the time is correspondingly reduced. It is preferred therefore to utilize spheres having a diameter not greater than about 0.005 inch and preferably of much smaller diameter, such as 0.001 inch or less.

The ordinary liquid detergents are generally solvents for nitrocellulose and are admirably suited as the plastisol solvent in the present process, it onlybeing necessary that such deterrent be a relatively slow acting solvent for the propellant at ordinary room or low tem- In other words, the solvent power of such solution of the propellant at ordinary temperatures during the time required for uniformly mixing the solvent and propellant together. Furthermore, if it is desired to prepare double base rocket powder grains, energizing modifiers, such as a liquid explosive nitric ester of a polyhydric alcohol, for example, nitroglycerine, butane triol trinitrate, diglycol dinitrate, ethylene glycol dinitrate, and the like, may be mixed with one or more miscible deterrents, such as dibutyl phthalate, dimethyl sebacate, dibutyl succinate, dibutyl adipate, triacetin,

ethyl 'diphenyl phosphate, tributyl phosphate, and the like, to provide plastisol solvents admirably suited for the purpose. If it is desired to produce single base rocket powder grains, the energizing modifier may be omitted from the composition and the plastisol solvent may be composed only of a liquid deterrent, such as one of those set forth above or mixtures of them. Other deterrents suitable therefor at temperatures above their melting point are dimethyl phthalate, dioctyl sebacate, ortho nitro biphenyl, butyl benzyl phthalate, octyl diphenyl phosphate, triethylene glycoldi-Z-ethyl butyrate (i.e. triglycol dihexoate), and the like.

' The amount of plastisol solventshould be such that it forms at least about 25% of the volume of a mixture of thei :soiven't ahd the propellant; f Substahtialtyi teseer 2 solution as the sodium sulphate derivative: et a ethythex-i' amounts at the iastisots'otventtend1o result in wide or i anoliisiadded tothe bath; :Qnehandred twenty-five pants 1 air pockets in the resulting rocket grain and :the mixture of sodium sulfate dissolvcd in 30a parts :of waterisz adde with ;s'uch lesser; amounts; is generally mat; sufficiently over? a: one hour period? and agitation continued for an.. :fiuid for the purpose :Greate'n amounts of ptastisoi sot additional three; hours; The globules are thenhardenedi went may? :be utilized to good advantage t increase the to form =pow'dr grains f by removal of it herethyl acetate: flliidiiy offthe mixture; fvaryithe :ballistie;properties of the during continuous agitationzand heating rupzto about: 99% Y rest1itin g rocketi grainz as desireihnd iinsure' absence of 1 accordance with the practice: set :forth :in =U.S=, Pat woids: or: air spaces in the grains=,zhut thezamount; utilized ent 2,021,114- ;referred :to,:i;hereinbcfore; r'li'he resultanb should preferably not be sarficientiy great to; result in: spherical pellets :of propellanthre: than air: dried at: 50 :segregation: or settling outzof the propeilant during the f I and are =co'm'posed: at; about 87;7%: nitrocellulose solutionzperiqdat elevated; temperature; j I f 11. idinitrotoiucne 20.3% catbotlf black; and 1.0% i 1 In operation, :the zplastisoi solvent is preferably desic ethyl centralize :and have: an average diameter: of acut 1 catedor otherwise treatedto reduceanytraces ofzmois'tu re f 0.091 inch; more or: less depending on the dcg re'eoff a'gi toaminiznum; and both the propellant =and=piastisoi soi tation used in the fforrnationi thereof, f 1 i I i f i are prezterahiyievacuated priorztomixing than abs abon t: 56.= 8=par t hy wei ght: of'isphen cahpellet iof :lute pressure ;of about tenfrniliimetefrs prices of mercury propellant; such as prepared by the; foregoing treating steps or: se e ai :hours and: then are intimately zmi xed any =e' the'ni piaced i a Sigma hladejm'ixer and: the sy'ste nimble m a z such as a Sigma biade: mixer; while the i evacuated to an absolute pressure iof about :ten :milli pressure: of aboutten: millimeters: or less? is maintained meters of mercury andiso held: for about sixteen fhours "Such precautians aszdesiecatinig and zevaeuetingare :prefer- Meanwhile; about 37: parts by weight at a substantially s" bse ved in under itri minimize the possibility? of nhanhydrous :ptainisei solvent; comp'flis'eid :et 74 by weight e'sirable :voidjsin the resnitin g extruded: powder grains. nitroglyce rine; 2i%-byweight dimethyl phtha'la e and he resultant: uniform mixture s; then heated; preferably by: weight ethyl :c'entralite'; is piaced: in af vessel: and the 2 19 1a fimpfirzature in: thearange; oi about 250 C.= to; 90: C

tar a: period f; time; snfifiaient; to: cause setutien hi the .propeliant; As za generall rule; the: higher the :terhper I :ture is; raised :during: this treatment the shorter? the period a mired for? salar es :of the propeitant and; the: tess pie sure; required: to: suhsequently ifo'rce the niix re through he ie: b pr a t n shouid be observed not to exceed he wmb n: or: explosive: temperature off the mixtur Whcn the propellant is: dissolved in :the :plastisai solv ent, .the;l 1ot: mass is t'orcgeckthrough :an; extrusion: die to; proidge a length or red of; explosive; the piece being contin I The heating ofit mixture employing? a5 heated: when i or he a mixture through the di mzil meters of mercur iandi so maintained for abnut six-= an hours: "The? :s'olv'ent sfthch added to the' prohalianfl theiniixer and the 'psr ated:to intiinatiy 'e solv ent an :propiciia ,1 lei t'aih'ejd ito pr'event entrapment Bot aiii tisol solvent has 5 a? specific? pcrcentage by: velmn'e: oh the pla'st s about 543390;? f After the Esoivent aha prepares are uniformly mixed; themixture is then barefuliy pour'eld Y or 'tn'ehwise ifiejcl into; the: heated :wo rrn br scrfe' :fied de .o'r passing the mix e ie'ngthib the screw:

stew: sedsr for;

fthat i i ee i s it s v -r ropeliahi ,Thz i fiXtrude approach to t he die is sameness/heats: to effect sheen? into suitable lengths to form extruded powder grains, tially complete solution ofthe propellant. It is thus poswhlch are of uniform composition throughout. sible to ca ry on the operation continuously. In order In order that the invention may be further clarified, 45 to accomplish this the screw feed mechanism is mainfollowing is an example illustrating a typical embodiment tained at a temperature of about to C. with the 0:15 the lnvention. Two hundred fifty parts by weight of rate of feeding thereto and discharge from the die being nitrocellulose having a nitrogen content of about 12.6% s ita y controlled to Permit Solution of the Prhpellahh are agitated with 4100 parts of water at about 50 C. to The exact time of such heat treatment required may vary form an aqueous slurry. A suspension of carbon black in 50 from a very few minutes up to several hours, and deethyl acetate is separately prepared by first thoroughly mixpends upon the activity of the solvent, the temperature mg 0.705 part of carbon black with parts of ethyl aceof the mixture, the particle size of the propellant, and the tate. Thls mixture of carbon black and ethyl acetate is effective resistance of the surface of the pro ellant grains, then added to 1250 parts more of ethyl acetate, and the her in fore des r b d as case h n but in y resultant dilute carbon black-ethyl acetate mixture are 55 event the mi xture is maintained at elevated temperature agitated to insure uniform distribution of the suspended for asufficicnt length of time to elfect a solution of the particles of carbon black. Thirty one and four-tenths propellant and sufficicnt setting up of the mass to permit parts of dlnltrotoluene and 2.8 parts of ethyl centralite fo mation of the desired powder grains. As the galaare then added to the carbon black-ethyl acetate mixture, tinized mass is extended from the die it is cut into powder When the dlnltrotoluenc and the ethyl centralitc are dis- 0 g of the desired lengthsolved, the resulti g mixture is then added to the nitro- Extruded p w er grains prep r d n accordance w cellulose slurry w h1lc the slurry is under agitation. The thfl foregoing example are of substantially uniform temperature 1s raised to 68 C. and the complete charge Position throughout the grain, and have the requisite vigorously ag tated for one hour at which time the nitrostrfihgth and other desirfid P y p p It will 1 cellulose 1s dissolved. Twenty-five parts of a protective 5 be apparent that the method is relatively Simple lending colloid of the type derlved from animal protein dispersed itself t0 mass Production and that Costly aliparahls n parts of water is then added and the agitation for developing high mixing pressures is needed- It will s continued untll the nitrocellulose solution is formed likewise be apparent that the limpellam and Plastisol Into globules of the desired small size. Vigorous agitasolvent y Vary pp y in composition and that l tlOn l S required in orderto form very small particles. The 70 nickel P W ma ns having substantially a V desired additlon f a emulsifying agent, h as h water 1 ballistic characteristics can be prepared in accordance ble salts of fatty acids su phonated oilsv the so-called with this invention- While the foregoing embodiment water-soluble o ls, and the like, greatly facilitates the forhas been Set forth in considerable detail, it is to be dismation of small particles of the nitrocellulose solution, tinctly understood that many modifications and variations and for this reason, twenty-four parts of a 40% aqueous 75 will naturally present themselves to those skilled in the art without departing from the spirit of this invention or the scope of the appended claims.

Having thus described the invention, what I claim and desire to secure by Letters Patent is:

1. In the art of making a powder grain, the process which comprises mixing fine particles of a gelatinized nitrocellulose propellant with a liquid plasticizer for the nitrocellulose selected from the group consisting of dibutyl phthalate, dimethyl sebacate, dibutyl succinate, dibutyl adipate, triacetin, ethyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, dioctyl sebacate, ortho nitro biphenyl, butyl benzyl phthalate, octyl diphenyl phosphate, and triethylene glycol di-Z-ethyl butyrate and mixtures thereof with a liquid explosive nitric ester of a polyhydric alcohol to form a substantially uniform pourable paste, said plasticizer liquid explosive nitric ester of a polyhydric alcohol mixture being present in an amount greater than about 25% by volume of the resulting paste, and simultaneously extruding said paste through a die and heating to completely dissolve said propellant in the plasticizer and thus effect solidification of said paste into a substantially homogeneous mass as it emerges from said die.

2. In the art of making powder grains, the process which comprises preparing a substantially uniform pourable paste by mixing together particles of gelatinized nitrocellulose propellant and a liquid plasticizer for nitrocellulose in the amount of at least about 25 percent by volume of the resulting mixture and at a temperature at which the nitrocellulose is substantially insoluble, raising the temperature of the resulting paste to a point where said particles are completely dissolved and have formed a substantially homogeneous mass, and thereafter forcing the mass through an extrusion die.

3. In the art of making powder grains, the process which comprises preparing a substantially uniform pourable paste by mixing together particles of gelatinized nitrocellulose propellant and a liquid plasticizer for nitrocellulose in the amount of at least about 25 percent by volume of the resulting mixture and at a temperature at which the nitrocellulose is substantially insoluble, raising the temperature of the resulting paste to a point where said particles are completely dissolved and have formed a substantially homogeneous mass, extruding said heated mass as a continuous piece, and thereafter subdividing said extruded piece into powder grain lengths.

4. In the art of making powder grains, the process which comprises preparing a substantially uniform pourable paste by mixing together particles of gelatinized nitrocellulose propellant and a liquid plasticizer for nitrocellulose in the amount of at least about 25 percent by volume of the resulting mixture and at a temperature at which the nitrocellulose propellant is substantially insoluble in the plasticizer, and thereafter heating said paste to a temperature within the range of from about 50 C. to about C. until the propellant particles have completely dissolved and formed a substantially homogeneous mass, and forcing the mass at said elevated temperature through an extrusion die.

5. In the art of making powder grains, the process which comprises preparing a substantially uniform pour able paste by mixing together particles of gelatinized nitrocellulose propellant and a liquid plasticizer for nitrocellulose in the amount of at least about 25 percent by volume of the resulting mixture and at a temperature at which the nitrocellulose propellant is substantially insoluble in the plasticizer, and thereafter simultaneously heating and extruding the paste through a suitable die at a temperature at which said particles completely dissolve in said plasticizer and the paste becomes solidified into a substantially homogeneous solid mass as it is forced through the die.

6. In the art of making powder grains, the process which comprises preparing a substantially uniform pourable paste by mixing together particles of gelatinized nitrocellulose propellant and a liquid plasticizer for nitro cellulose in the amount of at least about 25 percent by volume of the resulting mixture and at a temperature at which the nitrocellulose propellant is substantially insoluble in the plasticizer, said plasticizer including in its composition a liquid explosive nitric ester of a polyhydric alcohol, and thereafter heating said paste until the propellant particles have completely dissolved and formed a substantially homogeneous mass, and forcing the mass through an extrusion die.

7. In the art of making powder grains, the process which comprises preparing a substantially uniform pourable paste by mixing together particles of gelatinized nitrocellulose propellant having an average diameter of less than 0.005 inch and a liquid plasticizer for nitrocellulose in the amount of at least about 25 percent by volume of the resulting mixture and at a temperature at which the nitrocellulose propellant is substantially insoluble in the plasticizer, raising the temperature of the resulting paste to a point where said particles are completely dissolved and have formed a substantially homogeneous mass, and forcing the heated mass through an extrusion die.

References Cited in the file of this patent UNITED STATES PATENTS 2,027,114 Olsen et a1. Jan. 7, 1936 2,160,626 Schaefer May 30, 1939 2,210,871 Boddicker Aug. 6, 1940 2,292,469 Olsen Aug. 11, 1942 2,401,236 Fielitz May 28, 1946 2,417,090 Silk, et a1. Mar. 11, 1947 UNTTED STATES P. TENT OFFICE QERTIFTQATE 0F CG 1 RECTION December 15;, 1959 Patent No, 2,9l'? 379 7* Don W. Ryker appears in the-printed specification It is herebfi certified that error that the said Letters of the above numbered patent requiring correction and Patent should read as corrected below.

Column 2, line 4L2 ior' "detergents" read deterrents --g, I column 3 line 34 for 'plastisal read plastisol t column 4 line 5.5 for "*asufficient" read a sufficient extended read extruded 1' line 59 for Signed and sealed this 9th day of August 1960.

( SEAL) Attest:

KARL Ha AXLINE Attesting Officer ROBERT C. WATSON Commissioner of Patent UNITED S'IATES PATENT OFFICE @ERTIFICATE OF CORRECTION Patent No.a 2 9171379 December 15, 1959 Don W, Ryker It is herebj certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 42, for detergents read deterrents column 3., line 34 q for plastisal read plastisol column i line 55 for "*asufficient read a sufficient l line 59 for a i l extended read extruded Signed and sealed this 9th day of August 1960,

(SEAL) Attest:

KARL Ha AXLINE Attesting Ofiicer ROBERT c. WATSON Commissioner of Patents; 

1. IN THE ART OF MAKING A POWDER GRAIN, THE PROCESS WHICH COMPRISES MIXING FINE PARTICLES OF A GELATINEZED NITROCESSULOSE PROPELLANT WITH A LIQUID PLASTICIZER FOR THE NITROCELLULOSE SELECTED FROM THE GROUP CONSISTING OF DIBUTYL PHTHALATE, DIMETHYL SEBACATE, DIBUTHSISTING OF DIBUTYL ADIPATE, TRIACETIN,ETHYL DIPHENYL PHOSPHATE, TRIBUTYL PHOSPHATE, DIMETHYL PHTHALATE, DIOCTYL SEBACATE ORTHO NITRO BIPHENYL, BUTYL BENZYL PHTHALATE, OCTYL DIPHENYL PHOSPHATE, AND TRIETHYLENE GLYCOL DI-2-ETHYL BUTYRATE AND MIXTURES THEREOF WITH A LIQUID EXPLOSIVE NITRICESTER OF A POLYHYDRIC ALCOHOL TO FORM A SUBSTANTIALLY UNIFORM POURABLE PASTE, SAID PLASTICIZER LIQUID EXPLOSIVE NITRIC ESTER OF A POLYHYDRIC ALCOHOL MIXTURE BEING PRESENT IN AN AMOUNT GREATER THAN ABOUT 25% BY VOLUME OF THE RESULTING PASTE, AND SIMULTANEOUSLY EXTRUDING SAID PASTE THROUGH A DIE AND HEATING TO COMPLETELY DISSOLVE SAID PROPELLANT IN THE PLASTICIZER AND THUS EFFECT SOLIDIFICATION OF SAID PASTE INTO A SUBSTANTIALLY HOMOGENEOUS MASS AS IT EMERGES SAID DIE. 